Shapechanger. The mimic can use its action to polymorph into a wreath or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only). The mimic adheres to anything that touches it. A Large or smaller creature adhered to the mimic is also grappled by it (escape DC 12). Ability checks made to escape this grapple have disadvantage.

False Appearance (Object Form Only). While the mimic remains motionless, it is indistinguishable from an ordinary wreath.

Grappler. The mimic has advantage on attack rolls against any creature grappled by it.

The Holly and the Ivy. A creature that is grappled by the mimic is also restrained.  A creature that starts its turn grappled by the mimic takes 3 (1d6) piercing damage and must succeed on a DC 12 Constitution saving throw or be poisoned for 1 hour.  A creature can repeat this saving throw at the end of each of its turns, ending the effect on a success.

Innate Spellcasting. The mimic's innate spellcasting ability is Strength (spell save DC 12, +4 to hit with spell attacks).  The mimic can innately cast the following spells, requiring no components or concentration:

At will: druidcraft, thorn whip

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage plus 5 (2d4) damage, half of which (rounded up) is acid damage, while the other half (rounded down) is poison damage.

Berry Barrage (Recharge 5–6).  The mimic hurls holly berries from its branches in a 15-foot cone. Each creature in that area must make a DC 12 Dexterity saving throw.  On a failure, 3 (1d6) berries adhere to the target, or half as many berries (rounded down) on a success.  Each berry is actually a miniature mimic.  A berry mimic is a Tiny monstrosity with AC 6, 1 hit point, a 2 (−4) in every ability score, and a speed of 1 foot.  A berry mimic can be killed by normal means or scraped off using an action. At the end of each of the target's turns, the berry  mimics excrete a corrosive toxin, and the target takes 1 acid damage and 1 poison damage per berry mimic adhering to it.